Previous hoist ring mounting screws had been held in an assembled configuration with a thrust washer element, a bushing element, a rotatable body element, and a pivotally mounted lifting loop element by way of a snap ring or a retaining ring on the hoist ring mounting screw. The use of a snap ring in an annular groove on the shank of a mounting screw is disclosed, for example, in Tsui U.S. Pat. No. 5,405,210, and in Tsui et al. U.S. Pat. No. 4,641,986, both of which are hereby incorporated herein by reference as though fully set forth hereat. The use of a retention ring is disclosed, for example, in Chandler U.S. Pat. No. 5,352,056, which is hereby incorporated herein by reference as though fully set forth hereat.
Hoist rings are critical safety devices. Safety is the paramount concern when designing hoist rings. Workers in this art proceed very cautiously with design changes, and adopt changes only when they are proven to be safe and effective.
It is of concern to workers in this art that the hoist rings they design are mounted by the end users to the loads they are intended to lift. Precautions must be taken in the design process to insure insofar as possible that it is easy, simple, and straightforward for an end user to properly mount hoist rings to such loads. One such precaution involves designing hoist rings so that they are provided to the end user in a fully assembled configuration with all of the elements joined together in one assembly. This eliminates the risk that some element will be left out or that the hoist ring will be improperly assembled. Another design consideration has been to minimize the number of separate elements in the hoist ring. If an element is not present in the design, it cannot fail or be improperly installed.
The prior snap rings have served to hold the elements of hoist rings in a fully assembled configuration, but the snap rings themselves are separate elements. This adds to the complexity of the assembly. Also, there has been some concern that during handling, installation, or use, the snap rings might become separated from the hoist ring assemblies. If, for example, a snap ring were to be dislodged during installation it might lodge between the hoist ring assembly and the load to which it is attached. This might prevent the hoist ring from being properly tightened to a load. The same concerns apply to retention rings.
Those in the art concerned with such problems, and particularly those concerned with safety have long recognized the need to reduce the number of elements and secure them together so that the elements of hoist rings cannot become accidentally separated from one another. There is a need to eliminate as many separate elements from hoist ring assemblies as possible.